1. Field of the Invention
The present invention relates to manually operated liquid dispensing pump devices for use with consumer product containers; and more particularly, to such devices having a collapsible pump chamber (e.g., a bellows pump chamber).
2. Description of the Prior Art
Manually operated dispensing devices for pumping liquid from a supply container are widely known in the art. These liquid dispensers traditionally utilize a piston and cylinder pump chamber. A helical metal spring is generally utilized to provide the force necessary to return the piston to its initial position. Additional parts are generally related to an inlet valve, an outlet valve and a vent valve. Furthermore, in cases where a liquid spray discharge is desired, additional parts are often related to a swirl chamber. One disadvantage of such piston and cylinder dispensing devices is the great amount of sliding friction developed between the piston and the cylinder due to the tight telescopic fit required to maintain a fluid tight seal. Binding, may also occur between the piston and cylinder. Another disadvantage includes the relatively large number of parts such sprayers typically utilize which generally increases the cost of such pumps.
Consequently, attempts to utilize a manually compressible flexible pump chamber in place of the piston and cylinder have been made. For example, bellows have been utilized to replace the function of the piston, cylinder and return spring. Still other liquid dispensing devices have utilized a diaphragm or bladder as the manually compressible pump chamber. The use of such manually compressible pump chambers is substantially free of the sliding friction and the potential binding losses associated with the piston and cylinder.
One disadvantage associated with some pump devices utilizing such manually compressible flexible pump chambers (particularly, e.g., bellows) is that these chambers don't collapse completely; leaving a significant volume within the pump chamber upon complete compression. This compressed volume within the pump chamber can negatively impact performance of the pump device; e.g., priming.